1. Field of the Invention
The present invention relates generally to permanent magnet rotor alternators for internal combustion engines and more particularly to a permanent magnet rotor alternator wherein the rotor hub is an integral part of the flywheel/starting gear of the internal combustion engine.
2. Description of the Prior Art
Many automotive type alternators use wound stator and rotor assemblies. An electromagnetic force is produced in and around the rotor windings by admitting current through the rotor windings. As the magnetic field produced in the spinning rotor couples with the windings at the stator, current is induced in the stator windings. Alternators such as this require brushes or slip rings to maintain a closed circuit for admitting the current necessary m the rotor while it is spinning. These mechanical connections are vulnerable to wear and corrosion. Electrical noise is common as well, which may affect other sensitive electronics common to modern automobiles.
Permanent magnet rotor alternators do not require that a current be supplied to the rotor. The field inherent to, and generated by the magnetic material induces current in the stator as the magnet poles move in respect to the stator windings. Because current need not be supplied to the rotor, slip rings and brushes are not required. Hence, the noise and wear associated with these alternators employing these elements are eliminated.
It should be appreciated by those skilled in the art that, although traditional regulating means for wound rotor systems, e.g. control of field current in rotor windings, are not applicable to permanent magnet rotor alternators, other means, such as those implementing bipolar SCR devices, a bridge rectifier, and associated circuitry have been employed efficiently and reliably. Regulation is achieved by shorting the output current so as to not exceed the system requirements, while at the same time assuring that the battery does not become short circuited.
Permanent magnet rotor alternators and magnets have been used successfully for many years in small industrial engines and marine applications. While the rotor is often an integral part of a flywheel/starting gear, the prior art systems have several drawbacks. Typically, a cup-shaped rotor assembly is used. Individual magnets are attached to the "cup" at the inner rim, and an annular gear is welded or press-fit to the outer rim for allowing the gear to be driven by a starting motor. In systems such as this, the stator is internal to the rotor assembly, thereby leaving the external spinning rotor assembly exposed. This arrangement is bulky and presents potential hazards should a magnet become loose when spinning at high rpm. The loss of a magnet could make the system dynamically unstable as well. An additional shroud may be used to protect against a projected magnet, but a shroud adds to the bulk, expense, and complexity of the system. Examples of patented prior art devices may be seen in U.S. Pat. No. 4,345,553 (Magrane et al); U.S. Pat. No. 3,955,550, (Carlsson); U.S. Pat. No. 3,140,413, (Terry et al.); U.S. Pat. No. 2,976,439, (Kiekhaefer); U.S. Pat. No. 2,856,550 (Phelon).